1. Field of the Invention
The present invention relates to broadband antennas and elements therefore for transmission and reception of radio frequency communications singularly or in arrays for providing multiple broadcast and reception streams. More particularly, it relates to planar horn antenna elements which are capable of broadband reception and transmission and which are employable individually or using individual elements integrated into arrays.
In use for a multiple-input and multiple-output scheme or MIMO, the novel-formed elements of the array may be closely spaced and receive and transmit signals in a broad spectrum between a high and low frequency point. A succession of recesses and projections positioned along the edges of both nodes of the element forming the horn provide a means to increase the operational frequency bandwidth of the formed element to exceed what the wide and narrow points of the element would normally dictate. Additionally, a mode of the device positioning of intermediate projections and recesses along the edge provides a means for enhanced impedance matching.
2. Prior Art
Since the inception of cellular telephones, smart phones, HDTV, digital radios, and other devices operating in various areas of the available spectrum, service providers have had the task of installing a plurality of antenna sites over a geographic area to provide communications to subscribers. Some such antenna sites are singular and cover a broad area, some are small or cellular and employ many smaller antenna sites with each covering a smaller area of the whole.
From inception to the current mode of digital broadcasting and reception, providers have each installed their own plurality of large external antennas for such cell sites. Individual antenna sites may employ one or a plurality of antennas operating on different frequencies. In practice, cell sites are grouped in areas of high population density with the most potential users. Because each cellular service provider has their own system, each such provider will normally have their own antenna sites spaced about a geographic area to form the cells in their respective system. In suburban areas, the large dipole or mast type antennas must be placed within each cell. Such masts are commonly spaced 1-2 miles apart in suburban areas and in dense urban areas may be as close as ¼-½ miles apart.
Such RF antennas, be they for digital communications, cell phones or HDTV, employ antenna sites with large towers and large masts are generally considered eyesores by the public. Because each provider has their own system of cell sites, and because each geographic area has a plurality of providers, antenna blight is a common problem in many urban and suburban areas.
The many different service providers employ many different technologies such as GSM and CDMA using industry standards for 3G and 4G (short for 3rd and 4th generation). They also employ these technologies on bandwidths the provider either owns or leases, and which are adapted to the technologies. Consequently, the different carriers tend to operate on different frequencies and since conventional dipole and other cell antennas are large by conventional construction, even where the different providers are positioning sites near each other, they still have their own cell towers adapted to the length and configuration of the large antennas they employ for their systems and which are adapted to their individual broadcast and receiving bands in the RF spectrum.
Since the many carriers and technologies employ different sized, large antennas, even if they wanted to share cell sites and antennas more often, the nature of the antennas used conventionally discourages it. The result being a plethora of antenna sites, some right next to each other, with large ungainly and unsightly antennas on large towers which are aesthetically unpleasing.
In the case of 3G and 4G technologies, data is broadcast in multiple independent RF streams in schemes such as MIMO to communicate data and voice to and from multiple antennas adapted to handle the frequency of each stream. Antennas conventionally must be spaced from each other at least ½ a wavelength of the RF frequency on which they operate to avoid problems with interference. In the case of a broadband antenna with a low end frequency of 700 Mhz, this can be at least a 17 inch spacing requirement of each of the plurality of antenna elements from each other. This physical requirement can be overcome using multiplexing of adjacent antennas to turn them off when one antenna is in broadcast mode or using complicated and expensive smart antenna schemes and switching techniques. However, performance lacks and is prone to problems using such techniques. Additionally, physical spacing, if employed, renders the antenna array for multi stream use very large if the lower frequencies are in the 600-800 Mhz spectrum.
Radio communication sites and television broadcasting sites, and WiFi sites, and other RF communications sites operate on other frequencies and employ customized antennas for such which are not adaptable easily to receive and transmit other areas of the radio spectrum.
As such, there is a continuing unmet need for an improved antenna element which is configured to operate in a broadband fashion between a high and low frequency and at all frequencies therebetween. Such an element should be adaptable in constructional dimensions to allow for transmission and receipt of RF communications throughout the available spectrums by a simple reconfiguration of dimensions. Further, such an antenna element should be capable of formation into arrays to increase their effectiveness.
Further, such an array should allow for close spacing of the antenna elements of the array and concurrent reception and broadcast by the multiple antennas closely spaced in the array, without complicated switching or multiplexing. Further, such a device should employ individual antenna elements which provide a very high potential for the as-needed configuration for frequency, frequency rejection, polarization, gain, direction, steering, impedance matching, and low spectrum enhancement, and other factors desired in a cellular system for the varying servicing requirements of varying numbers of users over a day's time.
Further, such a device should employ a wideband antenna radiator element able to service all of the frequencies employed by the multiple carriers from 470-860 Mhz, 680-2000 Mhz, 2-6 Ghz, 6-18 Ghz, 18-40 Ghz, and 40-100 Ghz, or in segments between 700 Mhz to 2100 Mhz. Ideally, such an antenna or element should allow for increased operational frequencies through the provision of novel edge shapes to a formed horn antenna to thereby maximize the ability of elements and arrays of such elements to send and receive RF signals from their mounted positions.
Finally, because impedance matching is so important to the ultimate performance of any antenna element, such an element should provide additional means to adjust component parts forming the element to change the required matching for the element and the task assigned it.